【Objective】With clinical experience, nurses develop expertise in their motor and cognitive skills to perform required nursing care. Is there a relationship between years of clinical experience and the cognitive processes used in clinical decision making? The purpose of this study is to examine the relationship between clinical experience and Line-Of-Reasoning (Argument, Triggering cues, Domain concepts, Intermediate conclusion, Intermediate action, and Conclusion which relate to clinical decision making among 5〜6 years of clinical experience group, 7〜9 years of clinical experience group, and 10〜13 years of clinical experience group.【Method】A think aloud method was used to collect verbal data using three written cases developed by the investigators. The participants' verbalizations were audio taped and transcribed for Protocol Analysis.【Participants and setting】Twenty six clinical nurses (all females with clinical experiences from 5 years to 13 years ; 5〜6 years=12,7〜9 years=6,10〜13years=8) were recruited from 3 university hospitals and 1 public general hospital in Kansai and Shikoku metropolitan areas. All of them agreed to participate in the study as a volunteer.【Findings】A repeated measures analysis of variance(ANOVA) showed a significant main effect for the clinical experiences in Triggering cues(F_<2,387>(.01)=5.81), Domain concepts(F_<2,387>(.01)=17.10), Intermediate conclusion(F_<2,387>(.01)=18.74), Intermediate action(F_<2,387>(.01)=17.53), and Conclusion(F_<2,387>(.01)=14.41). The effects of the clinical experiences in Conclusion differ significantly between 5〜6 years group and 10〜13 years group, and between 7〜9 years group and 10〜13 years.【Conclusion】Findings from this study indicate that among the proficient nurses, the ability to make clinical decision based on Triggering cues and knowledge gained from experience is related to number of years of clinical experience.